There is a need in the semiconductor technology for a solder interconnection structure that will resist thermal migration and also exhibit the ductility to accommodate stresses due to coefficient of expansion differences between the material of the semiconductor device and the substrate.
Integrated circuit devices whether individual active devices, individual passive devices, multiple active devices within a single chip, or multiple passive and active devices within a single chip, require suitable input/output connections between themselves and other circuit elements or structures. These devices are typically very small and fragile. Because of their size and fragility,they are commonly carried on substrates for support. Interconnection of these devices to the substrate is a particular problem. A number of interconnection requirements must be fulfilled before the resultant connection is acceptable.
Thermal bonding processes which are widely employed to make electrical contact to semiconductor devices fail to meet one or more of the following criteria: One criteria is that the interconnection must have sufficient strength to withstand normal shock and vibration associated with information handling systems. Another criteria is that the connecting material must not deteriorate or change electrical or mechanical characteristics when tested under extreme humidity or temperature conditions. Additionally the interconnection must not short circuit the semiconductor. The interconnection must also have a melting point sufficiently high that it will not be affected during any soldering of the substrate to a supporting card. Finally, the connecting material should not produce a doping action on the active and passive chip devices with which the substrate is associated.
The use of a ductile solder pad to support chip devices has been proposed to reduce the transmission of thermal and mechanical stresses to the joint between the pad and the chip device. Such solder pad connections are disclosed and claimed in U.S. Pat. No. 3,495,133. Solder connections are also described in detail in an article entitled "SLT Device Metallurgy and its Monolithic Extension" by P. Totta and R. Sopher in the IBM Journal of Research and Development, Vol. 13 No. 3, May 1969 P. 226 to 238.
These solder connections have proven very successful for electrically joining highly integrated semiconductor devices with numerous input/output pads to suitable supporting substrates. This invention is an improved solder connection adapted for use in highly integrated semiconductor devices operating at high power levels where significant amounts of heat are generated by and within the device. The solder connection is adapted to operate for long periods of time under highly stressed conditions.